Fragment from an interview with Gerhard Richter by Robert Storr (2002) in “Gerhard Richter Forty Years Of Painting” edited by The Museum Of Modern Art:

Bruce Nauman once made a neon with the text, “The true artist helps the world by revealing mystic truths” which he put in the window of his studio like a beer sign. That piece was addressed both to himself and to the public. (…) And what appeared to be a declaration was really a question: “Do you believe this? Do you believe this?”